Like you, i sight fish quite a lot.
As I got older, I needed glasses for reading and then I needed a slight magnification for fairly close up day to day stuff, so i use varifocals for normal wear at work.
Thinking they would be OK for fishing, i had a pair of polarised varifocal glasses made, but found I couldn't get on with them on uneven ground due to having to look down through the high magnification section.
Now I use single vision prescription sunglasses and use flip down magnifiers for tying on flies and sorting tangles. I have one pair for low light and a darker pair fur sunny days
Hope that helps.
Alex
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Laguna Bay II Condominium Pattaya